UrlTemplateImageryProvider.js

define([
        '../Core/Cartesian2',
        '../Core/Cartesian3',
        '../Core/Cartographic',
        '../Core/combine',
        '../Core/Credit',
        '../Core/defaultValue',
        '../Core/defined',
        '../Core/defineProperties',
        '../Core/DeveloperError',
        '../Core/Event',
        '../Core/GeographicProjection',
        '../Core/isArray',
        '../Core/Math',
        '../Core/Rectangle',
        '../Core/Resource',
        '../Core/WebMercatorTilingScheme',
        '../ThirdParty/when',
        './ImageryProvider'
    ], function(
        Cartesian2,
        Cartesian3,
        Cartographic,
        combine,
        Credit,
        defaultValue,
        defined,
        defineProperties,
        DeveloperError,
        Event,
        GeographicProjection,
        isArray,
        CesiumMath,
        Rectangle,
        Resource,
        WebMercatorTilingScheme,
        when,
        ImageryProvider) {
    'use strict';

    var templateRegex = /{[^}]+}/g;

    var tags = {
        'x': xTag,
        'y': yTag,
        'z': zTag,
        's': sTag,
        'reverseX': reverseXTag,
        'reverseY': reverseYTag,
        'reverseZ': reverseZTag,
        'westDegrees': westDegreesTag,
        'southDegrees': southDegreesTag,
        'eastDegrees': eastDegreesTag,
        'northDegrees': northDegreesTag,
        'westProjected': westProjectedTag,
        'southProjected': southProjectedTag,
        'eastProjected': eastProjectedTag,
        'northProjected': northProjectedTag,
        'width': widthTag,
        'height': heightTag
    };

    var pickFeaturesTags = combine(tags, {
        'i' : iTag,
        'j' : jTag,
        'reverseI' : reverseITag,
        'reverseJ' : reverseJTag,
        'longitudeDegrees' : longitudeDegreesTag,
        'latitudeDegrees' : latitudeDegreesTag,
        'longitudeProjected' : longitudeProjectedTag,
        'latitudeProjected' : latitudeProjectedTag,
        'format' : formatTag
    });

    /**
     * Provides imagery by requesting tiles using a specified URL template.
     *
     * @alias UrlTemplateImageryProvider
     * @constructor
     *
     * @param {Promise.<Object>|Object} [options] Object with the following properties:
     * @param {Resource|String} options.url  The URL template to use to request tiles.  It has the following keywords:
     * <ul>
     *     <li><code>{z}</code>: The level of the tile in the tiling scheme.  Level zero is the root of the quadtree pyramid.</li>
     *     <li><code>{x}</code>: The tile X coordinate in the tiling scheme, where 0 is the Westernmost tile.</li>
     *     <li><code>{y}</code>: The tile Y coordinate in the tiling scheme, where 0 is the Northernmost tile.</li>
     *     <li><code>{s}</code>: One of the available subdomains, used to overcome browser limits on the number of simultaneous requests per host.</li>
     *     <li><code>{reverseX}</code>: The tile X coordinate in the tiling scheme, where 0 is the Easternmost tile.</li>
     *     <li><code>{reverseY}</code>: The tile Y coordinate in the tiling scheme, where 0 is the Southernmost tile.</li>
     *     <li><code>{reverseZ}</code>: The level of the tile in the tiling scheme, where level zero is the maximum level of the quadtree pyramid.  In order to use reverseZ, maximumLevel must be defined.</li>
     *     <li><code>{westDegrees}</code>: The Western edge of the tile in geodetic degrees.</li>
     *     <li><code>{southDegrees}</code>: The Southern edge of the tile in geodetic degrees.</li>
     *     <li><code>{eastDegrees}</code>: The Eastern edge of the tile in geodetic degrees.</li>
     *     <li><code>{northDegrees}</code>: The Northern edge of the tile in geodetic degrees.</li>
     *     <li><code>{westProjected}</code>: The Western edge of the tile in projected coordinates of the tiling scheme.</li>
     *     <li><code>{southProjected}</code>: The Southern edge of the tile in projected coordinates of the tiling scheme.</li>
     *     <li><code>{eastProjected}</code>: The Eastern edge of the tile in projected coordinates of the tiling scheme.</li>
     *     <li><code>{northProjected}</code>: The Northern edge of the tile in projected coordinates of the tiling scheme.</li>
     *     <li><code>{width}</code>: The width of each tile in pixels.</li>
     *     <li><code>{height}</code>: The height of each tile in pixels.</li>
     * </ul>
     * @param {Resource|String} [options.pickFeaturesUrl] The URL template to use to pick features.  If this property is not specified,
     *                 {@link UrlTemplateImageryProvider#pickFeatures} will immediately returned undefined, indicating no
     *                 features picked.  The URL template supports all of the keywords supported by the <code>url</code>
     *                 parameter, plus the following:
     * <ul>
     *     <li><code>{i}</code>: The pixel column (horizontal coordinate) of the picked position, where the Westernmost pixel is 0.</li>
     *     <li><code>{j}</code>: The pixel row (vertical coordinate) of the picked position, where the Northernmost pixel is 0.</li>
     *     <li><code>{reverseI}</code>: The pixel column (horizontal coordinate) of the picked position, where the Easternmost pixel is 0.</li>
     *     <li><code>{reverseJ}</code>: The pixel row (vertical coordinate) of the picked position, where the Southernmost pixel is 0.</li>
     *     <li><code>{longitudeDegrees}</code>: The longitude of the picked position in degrees.</li>
     *     <li><code>{latitudeDegrees}</code>: The latitude of the picked position in degrees.</li>
     *     <li><code>{longitudeProjected}</code>: The longitude of the picked position in the projected coordinates of the tiling scheme.</li>
     *     <li><code>{latitudeProjected}</code>: The latitude of the picked position in the projected coordinates of the tiling scheme.</li>
     *     <li><code>{format}</code>: The format in which to get feature information, as specified in the {@link GetFeatureInfoFormat}.</li>
     * </ul>
     * @param {Object} [options.urlSchemeZeroPadding] Gets the URL scheme zero padding for each tile coordinate. The format is '000' where
     * each coordinate will be padded on the left with zeros to match the width of the passed string of zeros. e.g. Setting:
     * urlSchemeZeroPadding : { '{x}' : '0000'}
     * will cause an 'x' value of 12 to return the string '0012' for {x} in the generated URL.
     * It the passed object has the following keywords:
     * <ul>
     *  <li> <code>{z}</code>: The zero padding for the level of the tile in the tiling scheme.</li>
     *  <li> <code>{x}</code>: The zero padding for the tile X coordinate in the tiling scheme.</li>
     *  <li> <code>{y}</code>: The zero padding for the the tile Y coordinate in the tiling scheme.</li>
     *  <li> <code>{reverseX}</code>: The zero padding for the tile reverseX coordinate in the tiling scheme.</li>
     *  <li> <code>{reverseY}</code>: The zero padding for the tile reverseY coordinate in the tiling scheme.</li>
     *  <li> <code>{reverseZ}</code>: The zero padding for the reverseZ coordinate of the tile in the tiling scheme.</li>
     * </ul>
     * @param {String|String[]} [options.subdomains='abc'] The subdomains to use for the <code>{s}</code> placeholder in the URL template.
     *                          If this parameter is a single string, each character in the string is a subdomain.  If it is
     *                          an array, each element in the array is a subdomain.
     * @param {Credit|String} [options.credit=''] A credit for the data source, which is displayed on the canvas.
     * @param {Number} [options.minimumLevel=0] The minimum level-of-detail supported by the imagery provider.  Take care when specifying
     *                 this that the number of tiles at the minimum level is small, such as four or less.  A larger number is likely
     *                 to result in rendering problems.
     * @param {Number} [options.maximumLevel] The maximum level-of-detail supported by the imagery provider, or undefined if there is no limit.
     * @param {Rectangle} [options.rectangle=Rectangle.MAX_VALUE] The rectangle, in radians, covered by the image.
     * @param {TilingScheme} [options.tilingScheme=WebMercatorTilingScheme] The tiling scheme specifying how the ellipsoidal
     * surface is broken into tiles.  If this parameter is not provided, a {@link WebMercatorTilingScheme}
     * is used.
     * @param {Ellipsoid} [options.ellipsoid] The ellipsoid.  If the tilingScheme is specified,
     *                    this parameter is ignored and the tiling scheme's ellipsoid is used instead. If neither
     *                    parameter is specified, the WGS84 ellipsoid is used.
     * @param {Number} [options.tileWidth=256] Pixel width of image tiles.
     * @param {Number} [options.tileHeight=256] Pixel height of image tiles.
     * @param {Boolean} [options.hasAlphaChannel=true] true if the images provided by this imagery provider
     *                  include an alpha channel; otherwise, false.  If this property is false, an alpha channel, if
     *                  present, will be ignored.  If this property is true, any images without an alpha channel will
     *                  be treated as if their alpha is 1.0 everywhere.  When this property is false, memory usage
     *                  and texture upload time are potentially reduced.
     * @param {GetFeatureInfoFormat[]} [options.getFeatureInfoFormats] The formats in which to get feature information at a
     *                                 specific location when {@link UrlTemplateImageryProvider#pickFeatures} is invoked.  If this
     *                                 parameter is not specified, feature picking is disabled.
     * @param {Boolean} [options.enablePickFeatures=true] If true, {@link UrlTemplateImageryProvider#pickFeatures} will
     *        request the <code>options.pickFeaturesUrl</code> and attempt to interpret the features included in the response.  If false,
     *        {@link UrlTemplateImageryProvider#pickFeatures} will immediately return undefined (indicating no pickable
     *        features) without communicating with the server.  Set this property to false if you know your data
     *        source does not support picking features or if you don't want this provider's features to be pickable. Note
     *        that this can be dynamically overridden by modifying the {@link UriTemplateImageryProvider#enablePickFeatures}
     *        property.
     * @param {Object} [options.customTags] Allow to replace custom keywords in the URL template. The object must have strings as keys and functions as values.
     *
     *
     * @example
     * // Access Natural Earth II imagery, which uses a TMS tiling scheme and Geographic (EPSG:4326) project
     * var tms = new Cesium.UrlTemplateImageryProvider({
     *     url : 'https://cesiumjs.org/tilesets/imagery/naturalearthii/{z}/{x}/{reverseY}.jpg',
     *     credit : '© Analytical Graphics, Inc.',
     *     tilingScheme : new Cesium.GeographicTilingScheme(),
     *     maximumLevel : 5
     * });
     * // Access the CartoDB Positron basemap, which uses an OpenStreetMap-like tiling scheme.
     * var positron = new Cesium.UrlTemplateImageryProvider({
     *     url : 'http://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png',
     *     credit : 'Map tiles by CartoDB, under CC BY 3.0. Data by OpenStreetMap, under ODbL.'
     * });
     * // Access a Web Map Service (WMS) server.
     * var wms = new Cesium.UrlTemplateImageryProvider({
     *    url : 'https://programs.communications.gov.au/geoserver/ows?tiled=true&' +
     *          'transparent=true&format=image%2Fpng&exceptions=application%2Fvnd.ogc.se_xml&' +
     *          'styles=&service=WMS&version=1.1.1&request=GetMap&' +
     *          'layers=public%3AMyBroadband_Availability&srs=EPSG%3A3857&' +
     *          'bbox={westProjected}%2C{southProjected}%2C{eastProjected}%2C{northProjected}&' +
     *          'width=256&height=256',
     *    rectangle : Cesium.Rectangle.fromDegrees(96.799393, -43.598214999057824, 153.63925700000001, -9.2159219997013)
     * });
     * // Using custom tags in your template url.
     * var custom = new Cesium.UrlTemplateImageryProvider({
     *    url : 'https://yoururl/{Time}/{z}/{y}/{x}.png',
     *    customTags : {
     *        Time: function(imageryProvider, x, y, level) {
     *            return '20171231'
     *        }
     *    }
     * });
     *
     * @see ArcGisMapServerImageryProvider
     * @see BingMapsImageryProvider
     * @see GoogleEarthEnterpriseMapsProvider
     * @see createOpenStreetMapImageryProvider
     * @see SingleTileImageryProvider
     * @see createTileMapServiceImageryProvider
     * @see WebMapServiceImageryProvider
     * @see WebMapTileServiceImageryProvider
     */
    function UrlTemplateImageryProvider(options) {
        //>>includeStart('debug', pragmas.debug);
        if (!defined(options)) {
          throw new DeveloperError('options is required.');
        }
        if (!when.isPromise(options) && !defined(options.url)) {
          throw new DeveloperError('options is required.');
        }
        //>>includeEnd('debug');

        this._errorEvent = new Event();

        this._resource = undefined;
        this._urlSchemeZeroPadding = undefined;
        this._pickFeaturesResource = undefined;
        this._tileWidth = undefined;
        this._tileHeight = undefined;
        this._maximumLevel = undefined;
        this._minimumLevel = undefined;
        this._tilingScheme = undefined;
        this._rectangle = undefined;
        this._tileDiscardPolicy = undefined;
        this._credit = undefined;
        this._hasAlphaChannel = undefined;
        this._readyPromise = undefined;
        this._tags = undefined;
        this._pickFeaturesTags = undefined;

        /**
         * Gets or sets a value indicating whether feature picking is enabled.  If true, {@link UrlTemplateImageryProvider#pickFeatures} will
         * request the <code>options.pickFeaturesUrl</code> and attempt to interpret the features included in the response.  If false,
         * {@link UrlTemplateImageryProvider#pickFeatures} will immediately return undefined (indicating no pickable
         * features) without communicating with the server.  Set this property to false if you know your data
         * source does not support picking features or if you don't want this provider's features to be pickable.
         * @type {Boolean}
         * @default true
         */
        this.enablePickFeatures = true;

        this.reinitialize(options);
    }

    defineProperties(UrlTemplateImageryProvider.prototype, {
        /**
         * Gets the URL template to use to request tiles.  It has the following keywords:
         * <ul>
         *  <li> <code>{z}</code>: The level of the tile in the tiling scheme.  Level zero is the root of the quadtree pyramid.</li>
         *  <li> <code>{x}</code>: The tile X coordinate in the tiling scheme, where 0 is the Westernmost tile.</li>
         *  <li> <code>{y}</code>: The tile Y coordinate in the tiling scheme, where 0 is the Northernmost tile.</li>
         *  <li> <code>{s}</code>: One of the available subdomains, used to overcome browser limits on the number of simultaneous requests per host.</li>
         *  <li> <code>{reverseX}</code>: The tile X coordinate in the tiling scheme, where 0 is the Easternmost tile.</li>
         *  <li> <code>{reverseY}</code>: The tile Y coordinate in the tiling scheme, where 0 is the Southernmost tile.</li>
         *  <li> <code>{reverseZ}</code>: The level of the tile in the tiling scheme, where level zero is the maximum level of the quadtree pyramid.  In order to use reverseZ, maximumLevel must be defined.</li>
         *  <li> <code>{westDegrees}</code>: The Western edge of the tile in geodetic degrees.</li>
         *  <li> <code>{southDegrees}</code>: The Southern edge of the tile in geodetic degrees.</li>
         *  <li> <code>{eastDegrees}</code>: The Eastern edge of the tile in geodetic degrees.</li>
         *  <li> <code>{northDegrees}</code>: The Northern edge of the tile in geodetic degrees.</li>
         *  <li> <code>{westProjected}</code>: The Western edge of the tile in projected coordinates of the tiling scheme.</li>
         *  <li> <code>{southProjected}</code>: The Southern edge of the tile in projected coordinates of the tiling scheme.</li>
         *  <li> <code>{eastProjected}</code>: The Eastern edge of the tile in projected coordinates of the tiling scheme.</li>
         *  <li> <code>{northProjected}</code>: The Northern edge of the tile in projected coordinates of the tiling scheme.</li>
         *  <li> <code>{width}</code>: The width of each tile in pixels.</li>
         *  <li> <code>{height}</code>: The height of each tile in pixels.</li>
         * </ul>
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {String}
         * @readonly
         */
        url : {
            get : function() {
                return this._resource.url;
            }
        },

        /**
         * Gets the URL scheme zero padding for each tile coordinate. The format is '000' where each coordinate will be padded on
         * the left with zeros to match the width of the passed string of zeros. e.g. Setting:
         * urlSchemeZeroPadding : { '{x}' : '0000'}
         * will cause an 'x' value of 12 to return the string '0012' for {x} in the generated URL.
         * It has the following keywords:
         * <ul>
         *  <li> <code>{z}</code>: The zero padding for the level of the tile in the tiling scheme.</li>
         *  <li> <code>{x}</code>: The zero padding for the tile X coordinate in the tiling scheme.</li>
         *  <li> <code>{y}</code>: The zero padding for the the tile Y coordinate in the tiling scheme.</li>
         *  <li> <code>{reverseX}</code>: The zero padding for the tile reverseX coordinate in the tiling scheme.</li>
         *  <li> <code>{reverseY}</code>: The zero padding for the tile reverseY coordinate in the tiling scheme.</li>
         *  <li> <code>{reverseZ}</code>: The zero padding for the reverseZ coordinate of the tile in the tiling scheme.</li>
         * </ul>
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Object}
         * @readonly
         */
        urlSchemeZeroPadding : {
            get : function() {
                return this._urlSchemeZeroPadding;
            }
        },

        /**
         * Gets the URL template to use to use to pick features.  If this property is not specified,
         * {@link UrlTemplateImageryProvider#pickFeatures} will immediately returned undefined, indicating no
         * features picked.  The URL template supports all of the keywords supported by the
         * {@link UrlTemplateImageryProvider#url} property, plus the following:
         * <ul>
         *     <li><code>{i}</code>: The pixel column (horizontal coordinate) of the picked position, where the Westernmost pixel is 0.</li>
         *     <li><code>{j}</code>: The pixel row (vertical coordinate) of the picked position, where the Northernmost pixel is 0.</li>
         *     <li><code>{reverseI}</code>: The pixel column (horizontal coordinate) of the picked position, where the Easternmost pixel is 0.</li>
         *     <li><code>{reverseJ}</code>: The pixel row (vertical coordinate) of the picked position, where the Southernmost pixel is 0.</li>
         *     <li><code>{longitudeDegrees}</code>: The longitude of the picked position in degrees.</li>
         *     <li><code>{latitudeDegrees}</code>: The latitude of the picked position in degrees.</li>
         *     <li><code>{longitudeProjected}</code>: The longitude of the picked position in the projected coordinates of the tiling scheme.</li>
         *     <li><code>{latitudeProjected}</code>: The latitude of the picked position in the projected coordinates of the tiling scheme.</li>
         *     <li><code>{format}</code>: The format in which to get feature information, as specified in the {@link GetFeatureInfoFormat}.</li>
         * </ul>
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {String}
         * @readonly
         */
        pickFeaturesUrl : {
            get : function() {
                return this._pickFeaturesResource.url;
            }
        },

        /**
         * Gets the proxy used by this provider.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Proxy}
         * @readonly
         * @default undefined
         */
        proxy : {
            get : function() {
                return this._resource.proxy;
            }
        },

        /**
         * Gets the width of each tile, in pixels. This function should
         * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Number}
         * @readonly
         * @default 256
         */
        tileWidth : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('tileWidth must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._tileWidth;
            }
        },

        /**
         * Gets the height of each tile, in pixels.  This function should
         * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Number}
         * @readonly
         * @default 256
         */
        tileHeight: {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('tileHeight must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._tileHeight;
            }
        },

        /**
         * Gets the maximum level-of-detail that can be requested, or undefined if there is no limit.
         * This function should not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Number}
         * @readonly
         * @default undefined
         */
        maximumLevel : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('maximumLevel must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._maximumLevel;
            }
        },

        /**
         * Gets the minimum level-of-detail that can be requested.  This function should
         * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Number}
         * @readonly
         * @default 0
         */
        minimumLevel : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('minimumLevel must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._minimumLevel;
            }
        },

        /**
         * Gets the tiling scheme used by this provider.  This function should
         * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {TilingScheme}
         * @readonly
         * @default new WebMercatorTilingScheme()
         */
        tilingScheme : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('tilingScheme must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._tilingScheme;
            }
        },

        /**
         * Gets the rectangle, in radians, of the imagery provided by this instance.  This function should
         * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Rectangle}
         * @readonly
         * @default tilingScheme.rectangle
         */
        rectangle : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('rectangle must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._rectangle;
            }
        },

        /**
         * Gets the tile discard policy.  If not undefined, the discard policy is responsible
         * for filtering out "missing" tiles via its shouldDiscardImage function.  If this function
         * returns undefined, no tiles are filtered.  This function should
         * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {TileDiscardPolicy}
         * @readonly
         * @default undefined
         */
        tileDiscardPolicy : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('tileDiscardPolicy must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._tileDiscardPolicy;
            }
        },

        /**
         * Gets an event that is raised when the imagery provider encounters an asynchronous error.  By subscribing
         * to the event, you will be notified of the error and can potentially recover from it.  Event listeners
         * are passed an instance of {@link TileProviderError}.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Event}
         * @readonly
         */
        errorEvent : {
            get : function() {
                return this._errorEvent;
            }
        },

        /**
         * Gets a value indicating whether or not the provider is ready for use.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Boolean}
         * @readonly
         */
        ready : {
            get : function() {
                return defined(this._resource);
            }
        },

        /**
         * Gets a promise that resolves to true when the provider is ready for use.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Promise.<Boolean>}
         * @readonly
         */
        readyPromise : {
            get : function() {
                return this._readyPromise;
            }
        },

        /**
         * Gets the credit to display when this imagery provider is active.  Typically this is used to credit
         * the source of the imagery.  This function should not be called before {@link UrlTemplateImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Credit}
         * @readonly
         * @default undefined
         */
        credit : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('credit must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._credit;
            }
        },

        /**
         * Gets a value indicating whether or not the images provided by this imagery provider
         * include an alpha channel.  If this property is false, an alpha channel, if present, will
         * be ignored.  If this property is true, any images without an alpha channel will be treated
         * as if their alpha is 1.0 everywhere.  When this property is false, memory usage
         * and texture upload time are reduced.  This function should
         * not be called before {@link ImageryProvider#ready} returns true.
         * @memberof UrlTemplateImageryProvider.prototype
         * @type {Boolean}
         * @readonly
         * @default true
         */
        hasAlphaChannel : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this.ready) {
                    throw new DeveloperError('hasAlphaChannel must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');
                return this._hasAlphaChannel;
            }
        }
    });

    /**
     * Reinitializes this instance.  Reinitializing an instance already in use is supported, but it is not
     * recommended because existing tiles provided by the imagery provider will not be updated.
     *
     * @param {Promise.<Object>|Object} options Any of the options that may be passed to the {@link UrlTemplateImageryProvider} constructor.
     */
    UrlTemplateImageryProvider.prototype.reinitialize = function(options) {
        var that = this;
        that._readyPromise = when(options).then(function(properties) {
            //>>includeStart('debug', pragmas.debug);
            if (!defined(properties)) {
                throw new DeveloperError('options is required.');
              }
            if (!defined(properties.url)) {
                throw new DeveloperError('options.url is required.');
            }
            //>>includeEnd('debug');

            var customTags = properties.customTags;
            var allTags = combine(tags, customTags);
            var allPickFeaturesTags = combine(pickFeaturesTags, customTags);
            var resource = Resource.createIfNeeded(properties.url);
            var pickFeaturesResource = Resource.createIfNeeded(properties.pickFeaturesUrl);

            that.enablePickFeatures = defaultValue(properties.enablePickFeatures, that.enablePickFeatures);
            that._urlSchemeZeroPadding = defaultValue(properties.urlSchemeZeroPadding, that.urlSchemeZeroPadding);
            that._tileDiscardPolicy = properties.tileDiscardPolicy;
            that._getFeatureInfoFormats = properties.getFeatureInfoFormats;

            that._subdomains = properties.subdomains;
            if (isArray(that._subdomains)) {
                that._subdomains = that._subdomains.slice();
            } else if (defined(that._subdomains) && that._subdomains.length > 0) {
                that._subdomains = that._subdomains.split('');
            } else {
                that._subdomains = ['a', 'b', 'c'];
            }

            that._tileWidth = defaultValue(properties.tileWidth, 256);
            that._tileHeight = defaultValue(properties.tileHeight, 256);
            that._minimumLevel = defaultValue(properties.minimumLevel, 0);
            that._maximumLevel = properties.maximumLevel;
            that._tilingScheme = defaultValue(properties.tilingScheme, new WebMercatorTilingScheme({ ellipsoid : properties.ellipsoid }));
            that._rectangle = defaultValue(properties.rectangle, that._tilingScheme.rectangle);
            that._rectangle = Rectangle.intersection(that._rectangle, that._tilingScheme.rectangle);
            that._hasAlphaChannel = defaultValue(properties.hasAlphaChannel, true);

            var credit = properties.credit;
            if (typeof credit === 'string') {
                credit = new Credit(credit);
            }
            that._credit = credit;

            that._resource = resource;
            that._tags = allTags;
            that._pickFeaturesResource = pickFeaturesResource;
            that._pickFeaturesTags = allPickFeaturesTags;

            return true;
        });
    };

    /**
     * Gets the credits to be displayed when a given tile is displayed.
     *
     * @param {Number} x The tile X coordinate.
     * @param {Number} y The tile Y coordinate.
     * @param {Number} level The tile level;
     * @returns {Credit[]} The credits to be displayed when the tile is displayed.
     *
     * @exception {DeveloperError} <code>getTileCredits</code> must not be called before the imagery provider is ready.
     */
    UrlTemplateImageryProvider.prototype.getTileCredits = function(x, y, level) {
        //>>includeStart('debug', pragmas.debug);
        if (!this.ready) {
            throw new DeveloperError('getTileCredits must not be called before the imagery provider is ready.');
        }
        //>>includeEnd('debug');
        return undefined;
    };

    /**
     * Requests the image for a given tile.  This function should
     * not be called before {@link UrlTemplateImageryProvider#ready} returns true.
     *
     * @param {Number} x The tile X coordinate.
     * @param {Number} y The tile Y coordinate.
     * @param {Number} level The tile level.
     * @param {Request} [request] The request object. Intended for internal use only.
     * @returns {Promise.<Image|Canvas>|undefined} A promise for the image that will resolve when the image is available, or
     *          undefined if there are too many active requests to the server, and the request
     *          should be retried later.  The resolved image may be either an
     *          Image or a Canvas DOM object.
     */
    UrlTemplateImageryProvider.prototype.requestImage = function(x, y, level, request) {
        //>>includeStart('debug', pragmas.debug);
        if (!this.ready) {
            throw new DeveloperError('requestImage must not be called before the imagery provider is ready.');
        }
        //>>includeEnd('debug');
        return ImageryProvider.loadImage(this, buildImageResource(this, x, y, level, request));
    };

    /**
     * Asynchronously determines what features, if any, are located at a given longitude and latitude within
     * a tile.  This function should not be called before {@link ImageryProvider#ready} returns true.
     *
     * @param {Number} x The tile X coordinate.
     * @param {Number} y The tile Y coordinate.
     * @param {Number} level The tile level.
     * @param {Number} longitude The longitude at which to pick features.
     * @param {Number} latitude  The latitude at which to pick features.
     * @return {Promise.<ImageryLayerFeatureInfo[]>|undefined} A promise for the picked features that will resolve when the asynchronous
     *                   picking completes.  The resolved value is an array of {@link ImageryLayerFeatureInfo}
     *                   instances.  The array may be empty if no features are found at the given location.
     *                   It may also be undefined if picking is not supported.
     */
    UrlTemplateImageryProvider.prototype.pickFeatures = function(x, y, level, longitude, latitude) {
        //>>includeStart('debug', pragmas.debug);
        if (!this.ready) {
            throw new DeveloperError('pickFeatures must not be called before the imagery provider is ready.');
        }
        //>>includeEnd('debug');

        if (!this.enablePickFeatures || !defined(this._pickFeaturesResource) || this._getFeatureInfoFormats.length === 0) {
            return undefined;
        }

        var formatIndex = 0;

        var that = this;

        function handleResponse(format, data) {
            return format.callback(data);
        }

        function doRequest() {
            if (formatIndex >= that._getFeatureInfoFormats.length) {
                // No valid formats, so no features picked.
                return when([]);
            }

            var format = that._getFeatureInfoFormats[formatIndex];
            var resource = buildPickFeaturesResource(that, x, y, level, longitude, latitude, format.format);

            ++formatIndex;

            if (format.type === 'json') {
                return resource.fetchJson().then(format.callback).otherwise(doRequest);
            } else if (format.type === 'xml') {
                return resource.fetchXML().then(format.callback).otherwise(doRequest);
            } else if (format.type === 'text' || format.type === 'html') {
                return resource.fetchText().then(format.callback).otherwise(doRequest);
            }
            return resource.fetch({
                responseType: format.format
            }).then(handleResponse.bind(undefined, format)).otherwise(doRequest);
        }

        return doRequest();
    };

    var degreesScratchComputed = false;
    var degreesScratch = new Rectangle();
    var projectedScratchComputed = false;
    var projectedScratch = new Rectangle();

    function buildImageResource(imageryProvider, x, y, level, request) {
        degreesScratchComputed = false;
        projectedScratchComputed = false;

        var resource = imageryProvider._resource;
        var url = resource.getUrlComponent(true);
        var allTags = imageryProvider._tags;
        var templateValues = {};

        var match = url.match(templateRegex);
        if (defined(match)) {
            match.forEach(function(tag) {
                var key = tag.substring(1, tag.length - 1); //strip {}
                if (defined(allTags[key])) {
                    templateValues[key] = allTags[key](imageryProvider, x, y, level);
                }
            });
        }

        return resource.getDerivedResource({
            request: request,
            templateValues: templateValues
        });
    }

    var ijScratchComputed = false;
    var ijScratch = new Cartesian2();
    var longitudeLatitudeProjectedScratchComputed = false;

    function buildPickFeaturesResource(imageryProvider, x, y, level, longitude, latitude, format) {
        degreesScratchComputed = false;
        projectedScratchComputed = false;
        ijScratchComputed = false;
        longitudeLatitudeProjectedScratchComputed = false;

        var resource = imageryProvider._pickFeaturesResource;
        var url = resource.getUrlComponent(true);
        var allTags = imageryProvider._pickFeaturesTags;
        var templateValues = {};
        var match = url.match(templateRegex);
        if (defined(match)) {
            match.forEach(function(tag) {
                var key = tag.substring(1, tag.length - 1); //strip {}
                if (defined(allTags[key])) {
                    templateValues[key] = allTags[key](imageryProvider, x, y, level, longitude, latitude, format);
                }
            });
        }

        return resource.getDerivedResource({
            templateValues: templateValues
        });
    }

    function padWithZerosIfNecessary(imageryProvider, key, value) {
        if (imageryProvider &&
            imageryProvider.urlSchemeZeroPadding &&
            imageryProvider.urlSchemeZeroPadding.hasOwnProperty(key) )
        {
            var paddingTemplate = imageryProvider.urlSchemeZeroPadding[key];
            if (typeof paddingTemplate === 'string') {
                var paddingTemplateWidth = paddingTemplate.length;
                if (paddingTemplateWidth > 1) {
                    value = (value.length >= paddingTemplateWidth) ? value : new Array(paddingTemplateWidth - value.toString().length + 1).join('0') + value;
                }
            }
        }
        return value;
    }

    function xTag(imageryProvider, x, y, level) {
        return padWithZerosIfNecessary(imageryProvider, '{x}', x);
    }

    function reverseXTag(imageryProvider, x, y, level) {
        var reverseX = imageryProvider.tilingScheme.getNumberOfXTilesAtLevel(level) - x - 1;
        return padWithZerosIfNecessary(imageryProvider, '{reverseX}', reverseX);
    }

    function yTag(imageryProvider, x, y, level) {
        return padWithZerosIfNecessary(imageryProvider, '{y}', y);
    }

    function reverseYTag(imageryProvider, x, y, level) {
        var reverseY = imageryProvider.tilingScheme.getNumberOfYTilesAtLevel(level) - y - 1;
        return padWithZerosIfNecessary(imageryProvider, '{reverseY}', reverseY);
    }

    function reverseZTag(imageryProvider, x, y, level) {
        var maximumLevel = imageryProvider.maximumLevel;
        var reverseZ = defined(maximumLevel) && level < maximumLevel ? maximumLevel - level - 1 : level;
        return padWithZerosIfNecessary(imageryProvider, '{reverseZ}', reverseZ);
    }

    function zTag(imageryProvider, x, y, level) {
        return padWithZerosIfNecessary(imageryProvider, '{z}', level);
    }

    function sTag(imageryProvider, x, y, level) {
        var index = (x + y + level) % imageryProvider._subdomains.length;
        return imageryProvider._subdomains[index];
    }

    function computeDegrees(imageryProvider, x, y, level) {
        if (degreesScratchComputed) {
            return;
        }

        imageryProvider.tilingScheme.tileXYToRectangle(x, y, level, degreesScratch);
        degreesScratch.west = CesiumMath.toDegrees(degreesScratch.west);
        degreesScratch.south = CesiumMath.toDegrees(degreesScratch.south);
        degreesScratch.east = CesiumMath.toDegrees(degreesScratch.east);
        degreesScratch.north = CesiumMath.toDegrees(degreesScratch.north);

        degreesScratchComputed = true;
    }

    function westDegreesTag(imageryProvider, x, y, level) {
        computeDegrees(imageryProvider, x, y, level);
        return degreesScratch.west;
    }

    function southDegreesTag(imageryProvider, x, y, level) {
        computeDegrees(imageryProvider, x, y, level);
        return degreesScratch.south;
    }

    function eastDegreesTag(imageryProvider, x, y, level) {
        computeDegrees(imageryProvider, x, y, level);
        return degreesScratch.east;
    }

    function northDegreesTag(imageryProvider, x, y, level) {
        computeDegrees(imageryProvider, x, y, level);
        return degreesScratch.north;
    }

    function computeProjected(imageryProvider, x, y, level) {
        if (projectedScratchComputed) {
            return;
        }

        imageryProvider.tilingScheme.tileXYToNativeRectangle(x, y, level, projectedScratch);

        projectedScratchComputed = true;
    }

    function westProjectedTag(imageryProvider, x, y, level) {
        computeProjected(imageryProvider, x, y, level);
        return projectedScratch.west;
    }

    function southProjectedTag(imageryProvider, x, y, level) {
        computeProjected(imageryProvider, x, y, level);
        return projectedScratch.south;
    }

    function eastProjectedTag(imageryProvider, x, y, level) {
        computeProjected(imageryProvider, x, y, level);
        return projectedScratch.east;
    }

    function northProjectedTag(imageryProvider, x, y, level) {
        computeProjected(imageryProvider, x, y, level);
        return projectedScratch.north;
    }

    function widthTag(imageryProvider, x, y, level) {
        return imageryProvider.tileWidth;
    }

    function heightTag(imageryProvider, x, y, level) {
        return imageryProvider.tileHeight;
    }

    function iTag(imageryProvider, x, y, level, longitude, latitude, format) {
        computeIJ(imageryProvider, x, y, level, longitude, latitude);
        return ijScratch.x;
    }

    function jTag(imageryProvider, x, y, level, longitude, latitude, format) {
        computeIJ(imageryProvider, x, y, level, longitude, latitude);
        return ijScratch.y;
    }

    function reverseITag(imageryProvider, x, y, level, longitude, latitude, format) {
        computeIJ(imageryProvider, x, y, level, longitude, latitude);
        return imageryProvider.tileWidth - ijScratch.x - 1;
    }

    function reverseJTag(imageryProvider, x, y, level, longitude, latitude, format) {
        computeIJ(imageryProvider, x, y, level, longitude, latitude);
        return imageryProvider.tileHeight - ijScratch.y - 1;
    }

    var rectangleScratch = new Rectangle();
    var longitudeLatitudeProjectedScratch = new Cartesian3();

    function computeIJ(imageryProvider, x, y, level, longitude, latitude, format) {
        if (ijScratchComputed) {
            return;
        }

        computeLongitudeLatitudeProjected(imageryProvider, x, y, level, longitude, latitude);
        var projected = longitudeLatitudeProjectedScratch;

        var rectangle = imageryProvider.tilingScheme.tileXYToNativeRectangle(x, y, level, rectangleScratch);
        ijScratch.x = (imageryProvider.tileWidth * (projected.x - rectangle.west) / rectangle.width) | 0;
        ijScratch.y = (imageryProvider.tileHeight * (rectangle.north - projected.y) / rectangle.height) | 0;
        ijScratchComputed = true;
    }

    function longitudeDegreesTag(imageryProvider, x, y, level, longitude, latitude, format) {
        return CesiumMath.toDegrees(longitude);
    }

    function latitudeDegreesTag(imageryProvider, x, y, level, longitude, latitude, format) {
        return CesiumMath.toDegrees(latitude);
    }

    function longitudeProjectedTag(imageryProvider, x, y, level, longitude, latitude, format) {
        computeLongitudeLatitudeProjected(imageryProvider, x, y, level, longitude, latitude);
        return longitudeLatitudeProjectedScratch.x;
    }

    function latitudeProjectedTag(imageryProvider, x, y, level, longitude, latitude, format) {
        computeLongitudeLatitudeProjected(imageryProvider, x, y, level, longitude, latitude);
        return longitudeLatitudeProjectedScratch.y;
    }

    var cartographicScratch = new Cartographic();

    function computeLongitudeLatitudeProjected(imageryProvider, x, y, level, longitude, latitude, format) {
        if (longitudeLatitudeProjectedScratchComputed) {
            return;
        }

        if (imageryProvider.tilingScheme.projection instanceof GeographicProjection) {
            longitudeLatitudeProjectedScratch.x = CesiumMath.toDegrees(longitude);
            longitudeLatitudeProjectedScratch.y = CesiumMath.toDegrees(latitude);
        } else {
            var cartographic = cartographicScratch;
            cartographic.longitude = longitude;
            cartographic.latitude = latitude;
            imageryProvider.tilingScheme.projection.project(cartographic, longitudeLatitudeProjectedScratch);
        }

        longitudeLatitudeProjectedScratchComputed = true;
    }

    function formatTag(imageryProvider, x, y, level, longitude, latitude, format) {
        return format;
    }

    return UrlTemplateImageryProvider;
});